A wearing type action assistance device is under development (see Patent Document 1 listed below). For example, when a person has an arm or a leg that does not easily work due to a disease of its joint or the joint does not easily work due to deterioration of a muscular power of the person, the person may wear this wearing type action assistance device by attaching an action assisting tool to the arm or the leg, in order to assist the action of the person around the joint.
This wearing type action assistance device is arranged to detect a myoelectricity signal that takes place according to a wearing person's intention, and arranged to generate a control signal to control a motor of the action assisting tool, based on the detected myoelectricity signal. Hence, the wearing type action assistance device enables a driving force of the action assisting tool to be transmitted to the arm or the leg as if by the wearing person's own muscular power.
When a walk action is performed by the wearing person, an assisting torque (assisting force) by the motor is controlled based on the detected myoelectricity signal as described above, and a position of a center of gravity (centroid position) of the wearing person according to the walk action is detected by measuring a load (weight) acting on the soles of the wearing person. The timing of outputting the assisting torque from the motor is adjusted in accordance with the walking speed of the wearing person and the timing of the alternate motions of the right and right feet. Thereby, the wearing person who receives the assisting torque from the motor is able to walk smoothly as if by the wearing person's own muscular power.
In a centroid position detector device according to the related art, a center-of-gravity sensor (reaction sensor) which detects a position of a center of gravity of a wearing person is attached to each of the soles of the wearing person. Using such sensors, the loads acting on the soles of the right and left feet accompanied with a walk action are detected, and a position of the center of gravity of the wearing person is determined based on changes of the loads on the soles of the right and left feet. As an example of the center-of-gravity sensor, for example, Patent Document 2 listed below discloses a plurality of pressure-sensitive sensors arranged to detect pressures of the weight acting on the right and left feet of a person.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-95561
Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-204730